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Earth Science Conservation Review
| Faughan and Dungiven Basins - The Murnies | Londonderry |
| Site number: | 499 | ||
| ESCC: | IS | ||
| Locality Type: | Inland exposure | Status: | TBC |
| Grid Reference: | C704052 Approximate | ||
| Google maps: | 54.88998,-6.90289 | ||
| County: | Londonderry | Council area: | Causeway Coast & Glens Borough Council |
| Period: | Quaternary | ||
| Site Description | |
|---|---|
| Description: | |
This glaciofluvial complex is situated on the northern foothills of the Sperrin Mountains 4km to the southeast of Dungiven, in the townlands of Hillhead and Tamniarin. It is characterised by two prominent, lobate flat-topped surfaces at 230 and 243m O.D., which cover an area of approximately 0.75km2. The north and northeast facing slopes are steep (35ยง) and the entire feature was covered by up to 3m of blanket bog and heath vegetation. The wedge-shaped unit of stratified sediments thickens northeast from the Altnaheglish meltwater channel which is incised into rock between Tamniarin and Teeavan Hills. Small meltwater channels occur along the lateral margins of the wedge. Overall, the flat-topped surfaces provide prominent skyline features when viewed westward from the main Dungiven/Glenshane Pass road. Internally, the deposit consists of two main units. About 90% consists of large-scale foresets of alternating sand and gravel beds which dip to the northeast. Clasts are predominately quartzites (99%) with a small schist component (1%). Foresets occur within broad channel-like structures. The frontal slopes of the feature are sub-parallel to the foreset dips. An angular unconformity separates the steeply dipping foresets from flat lying topset beds composed of poorly-sorted, matrix-supported, cobble gravels. Crude stratification is recorded by cobble lags, abrupt textural changes and shallow scours. At two locations ice wedge pseudomorphs up to 2m in depth by 0.6m across intrude into the bedding in the upper gravel beds. No major extensional faulting is present. The sediments have been intensively quarried for use mainly in the construction industry. The operation has continued at the site for over 20 years. The majority of the lower lobes and a small section of the upper level has been removed. A fraction of the blanket bog remains. Spoil heaps of unusable grade material, which now form the lateral slopes of the feature, dominate the view of the site from principal cross-valley vantage points i.e. the A6 Londonderry/Belfast road. | |
| Interpretation: | |
The deposit's structure is similar to a Gilbert-type delta which prograded northeastwards into a proglacial lake occupying the area of the present-day Glanrandal River valley. The rock-cut Altnasheskin meltwater channel acted as the main debris supply route from an ice lobe which wasted southwestwards across the local watershed between Teeavan and Tamniarin hills. Delta formation began with lake level at 243m O.D. but a drop in lake level resulted in incision and erosion of the upper delta surface and formation of a lower delta at 230m O.D. There is no evidence to suggest that ice in the Glenrandal valley was responsible for water ponding. It is more likely that Scottish ice blocked the upper Dungiven basin and the feature's steep slopes are primarily sedimentary and not ice-contact. | |
| Notes: | |
For site specific information on other sites within the Faughan and Dungiven Basins see the following sites: Key Site 500 - Faughan and Dungiven Basins - Derrynaflaw Key Site 501 - Faughan and Dungiven Basins - Banagher Key Site 502 - Faughan and Dungiven Basins - Templemoyle Key Site 503 - Faughan and Dungiven Basins - Tamnagh Key Site 504 - Faughan and Dungiven Basins - Cumber Key Site 505 - Faughan and Dungiven Basins - Gosheden Key Site 506 - Faughan and Dungiven Basins - Fawney Key Site 507 - Faughan and Dungiven Basins - Enagh For overview information and references on the Faughan and Dungiven Basins see the following site: Key Site 470 - Faughan and Dungiven Basins - Overview For general information and references on the sand and gravel landscapes of N. Ireland, and for directions to other regional sand and gravel sites, see the following site: Key Site 439 - Introduction to the Sand and Gravel Landscapes of N. Ireland | |
| Keywords | |
|---|---|
| Rocks: | Gravel, Sand |
| Relations: | Glacio-fluvial sediment |
| Geomorph: | deltaic foresets |
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Last updated: | 6 Jun 2005 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Faughan and Dungiven Basins - The Murnies, County Londonderry, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=499. Accessed on 2026-11-06. |
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